Electrical condenser



April 1942- J. A. KATER 2,279,826 ELECTRICAL CONDENSER Filed Dec. 20, 1938 INVZ'IVTOR J. A. KA TE R Patented Apr. -14, 1942 UNITED STATE s PATENT OFFICE ELECTRICAL CONDENSER Joseph A. Kater, Teaneck, N. 1., aaeignor to Bell Telephone laboratories, Incorporated, New York, N. Y., a orp ration of New York 2Claims.

This invention relates to electrical condensers and particularly to such condensers for use at high frequencies.

In apparatus operating at high frequencies, as for example in television systems where the frequency range may vary from 100 kilocycles to one or more megacycles, one of the problems to be solved is the reduction of the so-called parasitic effects such as the inductance between terminals of condensers in parallel combination with coils. Such inductances, though not appreciable at the lower frequencies, become very troublesome at frequencies of 100 kilocycles or more, and the effective inductance of several hundredths of a microhenry is quite appreciable.

It is therefore an object of the present invention to eliminate so far as possible the parasitic effect of inductance in condensers. particularly those for use in high frequency circuits. In accordance with the features of the present invention this object is attained by reducing to a minimum, for a given size unit, the physical dimensions of the inductive loop formed by the condenser terminals and plates and by positioning the terminal members in close proximity and in a non-inductive relation to each other.

The various features of the invention may be more clearly understood by reference to the accompanying drawing in which:

Fig. l discloses a condenser unit embodying the features of the invention encased in a suitable container;

Fig. 2 is a perspective view of unit of Fig. 1;

Fig. 3 is an exploded View showing the various elements in position to be assembled; and

Figs. 4 and 5 disclose the method of connecting the condenser plates together.

Referring particularly to Figs. 2 and 3 of the drawing the condenser unit disclosed comprises a'set of conducting plates 0- alternating with a set of similar conducting plates 'I-I and separated from each other by non-conducting plates 88 of suitable insulating material such as mica. The plates 6 are so displaced with respect to the insulating plates 0 that they extend away from them at one end, or the left end, as shown in the drawing. The plates 1, on the other hand, are so displaced as to extend on the opposite end of the mica sheets, or at the right on the drawing. One of the plates, plate I, extending in the same direction as plates 8 is provided with a terminal member III which is preferably integral therewith and a corresponding plate It alternating with plates 1 is provided with a similar terminal the condenser member 12. Sincethe thickness of the non-conducting plates of mica is of the order of .001 inch this terminal is provided with an offset portion II to provide a slight .separation between terminal-members. An insulating plate provided with an extended portion i4 is positioned between plates 9 and i I and similar insulating plates i5- it provided with corresponding extended portions are positioned at the ends of the stack. The conducting and non-conducting plates of the unit are then clamped between clamping plates l8 and I1 by means of screws ll passing through openings in plate l6 and engaging threaded openings in plate l'l. After the unit is clamped to the desired degree, the extended ends of the foil are brought together as shown in Fig. 4 and U-shaped clamping members lB-IQ are pressed over the ends of the foil to insure good electrical contact between all foils of a set, or the ends of the foils may be soldered together. The foil is then bent up at right angles as shown more clearly in Fig. 5 and the unit is ready to be placed in a container 2| provided with a'suitable cover 2| as shown in Fig. 1. The terminal members extend through suitable slits in a terminal strip 2! which may be of Bakelite or similar material and the cover portion ii is provided with an enlarged opening to eliminate any danger of short-cricuiting between terminals. When desired the unit may be impregnated or potted in accordance with conventional methods.

With the condenser unit assembled as described, the terminal members I! and II are in alignment and in close proximity to each other over substantially their entire length so that for electrical currents entering and leaving the condenser unit they form a non-inductive arrangement. Furthermore since the plates 9 and II are substantially superimposed parallel planes separated from each other only by the thickness of the mica insulation, the loop formed by the terminals and the plates is of minimum physical dimensions thereby largely eliminating any inductive effect. Condensers in accordance with this invention have been found to operate satisfactorily on high frequency circuits and they show a reduction in inductance of from to per cent and no measurable difference in other electrical characteristics as compared with conventional type condensers. Although any conventional material may be used for the condenser plates, terminals, clamping members, container and cover, it is preferable that all metals used in the construction be non-magnetic.

' parallel relation and in such close proximity to each other as to render them substantially noninductive.

2. An electrical condenser comprising a set of conducting plates or one polarity electrically joined together, a second set of conducting plates of opposite polarity to said first set electrically Joined together and alternating with the plates of said first set, a dielectric medium separating the plates of said first set from the plates of said second set, oneplate of said first set having a centrally positioned extension i'ormingthe tereminal for said set, an adjacent plate of said second set having a centrally positioned extension extending in the same direction and in alignment with said first extension and forming the terminal for said second set. said terminals being maintained in such close proximity as to reduce substantially the inductance between said terminals and plates.

JOSEPH A. KATER. 

